[Bug 26923] [InbandTracks] Number of HTML tracks from DASH

https://www.w3.org/Bugs/Public/show_bug.cgi?id=26923

--- Comment #5 from Bob Lund <b.lund@cablelabs.com> ---
(In reply to Cyril Concolato from comment #4)
> (In reply to Bob Lund from comment #3)
> > OK. Then this bug should be closed and marked as a duplicate of bug 26921.
> Part of this bug is a duplicate. Not all (see below). I don't want to close
> it.
> 
> > > > > Also, it is not clear which AS
> > > > > should be exposed ? All including those for which the mime type is not
> > > > > supported?
> > 
> > This question did not get addressed. It seems to make sense that the UA
> > should only create audio, video and non-metadata text tracks for media
> > streams it can render.
> Why would you only expose those tracks? Those tracks will be rendered. I
> agree standardization will help for interoperability in the UI. But
> standardization is even more important for the other tracks. The tracks that
> the browser cannot render. 

Those would be metadata text tracks. The spec already has language for which
AdaptationSet and ContentComponents result in the creation of metadata tracks.

As it stands now, the latest version [1] states exactly what constitutes an
HTML track based on AS or CC MIME type. We could add a note stating that that
the UA does not need to create tracks for audio/video MIME types that it cannot
render.

> Those are interesting to expose to JS so that JS
> app do something with them. That's also mentioned by Silvia in [3]
> "Exposing cues to JavaScript enables a Web developer to create all
> sorts of interesting presentations around it, such as interactive
> transcripts rendered next to the video."
> [3] http://lists.w3.org/Archives/Public/public-inbandtracks/2014Sep/0014.html
> 
> 
> > This bug was about creating tracks from the DASH MPD. Script created tracks
> > is another topic.
> I disagree.

The bug you submitted refers to UA.

> Scripts can be used to create tracks from the MPD. For the
> tracks that are known to be supported, rely on MSE, for others do it by hand.
> 

By hand, I assume you mean script. Yes, script can create text tracks.

> 
> > > Why? Informative specs are not really useful. It should be normative. UA
> > > don't have to implement it, but if they decide to implement it, it should be
> > > done in a normative way. The MSE follows that approach for instance, it says:
> > > "If an implementation claims to support a MIME type listed in the registry,
> > > its SourceBuffer implementation must conform to the byte stream format
> > > specification listed in the registry entry."
> > 
> > Feel free to go down that path.
> Fine. Thanks.

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Received on Tuesday, 14 October 2014 17:04:58 UTC